During the past several years, the popularity and viability of fuel cells for producing both large and small amounts of electricity has increased significantly. Fuel cells conduct an electrochemical reaction between chemicals such as hydrogen and oxygen to produce electricity and heat. Unlike batteries which store useable energy, fuel cells generate useable energy and are more easily “recharged” simply by replenishing the consumed fuel. Moreover, fuel cells are much cleaner and quieter than devices that combust hydrocarbons.
Fuel cells provide a direct current (DC) voltage that may be used to power motors, lights, computers, or any number of electrical appliances. While there are several different types of fuel cells, each using a different chemistry, fuel cells typically have three component parts: an anode, a cathode, and an electrolyte. Fuel cells are usually classified, depending on the type of electrolyte used, into one of five groups: alkaline fuel cells (AFC), phosphoric-acid fuel cells (PAFC), solid oxide fuel cells (SOFC), molten carbonate fuel cells (MCFC), and proton exchange membrane fuel cells (PEMFC). One variant of the PEMFC technology includes direct methanol fuel cells (DMFC), in which liquid methanol is directly fed to the fuel cell as fuel.
PEMFCs typically function by supplying hydrogen to an anode. The hydrogen provides protons to an electrolyte and releases electrons that pass through an external circuit to reach a cathode located opposite the anode. The protons solvate with water molecules and diffuse through the membrane to the cathode where they react with oxygen that has picked up electrons thereby forming water. PEMFCs have a number of distinct advantages over other fuel cells. PEMFCs have a very high power density (40% to 60% efficiency) and a very low operating temperature (around 80 degrees Celsius). Moreover PEMFCs do not utilized dangerous chemicals that may spill or leak. These qualities make PEMFCs extremely safe and low in maintenance requirements.
Traditionally, the proton exchange membrane (PEM) of a PEMFC has been formed by applying a solid semipermeable membrane to an electrode layer with an adhesive layer between the two. The membrane-adhesion layer electrode stack would then be compressed in the presence of heat to bond the layers together. However, traditional methods of forming PEM fuel cells tend to have a low amount of mechanical stability and are susceptible to swelling of the electrolyte. This swelling of the electrolyte often leads to increased fuel crossover resulting in degraded fuel efficiency of the fuel cell.